MyBatis-接口式编程

》1. 接口式编程：当接口和xml文件动态绑定时，MyBatis会为接口自动创建一个代理对象，通过代理对象去调用相应的方法。好处：解耦和，更安全的类型检查，明确的返回值
　　原生：　　　　IDao　　==>　　DaoImpl
　　Mybatis:　　IDao　　==>　　xxMapper.xml
》2.SqlSessionFactory：代表和数据库的一次会话，用完必须关闭；
　　SqlSessionFactory和Connection一样都是非线程安全的，每次使用都应该去获取新的对象；

1. 创建一个接口：

public interface EmployeeMapper {
    public Employee getEmpById(Long id) throws SQLException;
    public boolean add(Employee employee) throws SQLException ;
    public boolean edit(Employee employee) throws SQLException ;
    public boolean remove(Long id) throws SQLException ;
}

2. 创建Mapper映射文件：

　　》1.namespace:必须为接口的全类名
　　》2.sqlId与接口的方法名保持一致

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- 1.namespace:必须为接口的全类名 -->
<mapper namespace="cn.ll.mybatis.dao.EmployeeMapper">
    <!-- 2.sqlId与接口的方法名保持一致 -->
    <!-- public Employee getEmpById(Long id) -->
    <select id="getEmpById" resultType="Employee">
        select * from employee where eid = #{id}
    </select>
    <!-- public boolean add(Employee employee) -->
    <insert id="add" useGeneratedKeys="true" keyProperty="eid" >
        INSERT INTO employee(name,gender,email) VALUES(#{name},#{gender},#{email})
    </insert>
    <!-- public boolean edit(Employee employee) -->
    <update id="edit" >
        UPDATE employee SET name=#{name},gender=#{gender},email=#{email} WHERE eid=#{eid}
    </update>
    <!-- public boolean remove(Long id) -->
    <delete id="remove" >
        DELETE FROM employee WHERE eid=#{eid}
    </delete>
</mapper>

3. 加载配置文件进行测试：

@Test
public void test1() throws Exception {
    String resource = "mybatis/mybatis-config.xml";
    InputStream resourceAsStream = Resources.getResourceAsStream(resource);
    //1.获取SqlSessionFactory对象
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
    //2.获取SqlSession对象
    SqlSession session = sqlSessionFactory.openSession();
    try{//3.获取接口的实现类对象，当接口和xml文件动态绑定时，MyBatis会为接口自动创建一个代理对象，通过代理对象去调用相应的方法
        EmployeeMapper employeeMapper = session.getMapper(EmployeeMapper.class) ;
        Employee employee = employeeMapper.getEmpById(1L) ;
        System.out.println(employeeMapper + " ：" + employee);
    }finally {
        session.close();
    }
}